Same problem
apt-key list | grep -iB1 insync
pub 2048R/ACCAF35C 2012-09-10 [caducó: 2016-09-10]
uid Insynchq Inc services@insynchq.com
sudo apt-key adv --recv-keys --keyserver keys.gnupg.net ACCAF35C
no change
Ign http://apt.insynchq.com jessie/contrib Translation-en
Ign http://apt.insynchq.com jessie/non-free Translation-es
Ign http://apt.insynchq.com jessie/non-free Translation-en
Descargados 174 kB en 10s (17.3 kB/s)
Leyendo lista de paquetes… Hecho
W: Error de GPG: http://apt.insynchq.com jessie InRelease: Las siguientes firmas no fueron válidas: KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811